A BRYOPHYTE FLORA OF ESSEX 85
an area of 6000 acres and was made open to the public in 1878
(Buxton, 1911). Previously, as far back as 1600 it had covered
an area of 60,000 acres and must have supported a far more
varied flora than it does to-day. For example Edward Forster
(1765-1849) recorded Leucodon sciuroides, Antitrichia curtipen-
dula, Scleropodium tourretii, Cryphaea heteromalla, Rhytidia-
delphus triquetrus (very common), Orthotrichum striatum and
Ulota crispa. None of these has been recorded for the Forest for
at least fifty years.
Chittenden (1906) in a paper read to the Essex Field Club
suggested that the shortness of the Essex list was due to the fact
that only certain parts of the county had been carefully searched,
that it had low elevations and a lack of diversity of soils, the
small rainfall and the large amount of acid brought down by the
rain in many parts. We are still saying the same sixty years
later, although Dixon (1898) had 96 species and varieties for
North Essex and our records now show 246. The number of
species recorded goes hand in hand with the working bryologists.
Laundon (1967) in discussing the effects of air pollution on
lichens states that the polluted air of many towns prevents the
establishment of many species. It may be so with bryophytes,
but low humidity is an important factor. Laundon emphasizes
this when he states that in woods it is important to retain a thick
shrub layer, which provides shelter and so increases atmospheric
humidity, thus lowering evaporation rates. Eurynchium swartzii,
which likes hedgerows, being most frequent in calcareous dis-
tricts, grows round an overflow pipe on the rail viaduct in Water-
loo Bridge Road, London. It is not a moss that one would
expect to find in such a habitat. During the last two years it
has flourished in the same place. It is always moist and air
pollution does not seem to affect it. Coker (1967), in a paper on
the effects of sulphur dioxide pollution on bark epiphytes, is also
of the opinion that climatic dryness is at least as important a
factor. Courtney & Hardy (1967) working on an ecological sur-
vey of Wistman's Wood, Dartmoor, consider the interesting moss
Antitrichia curtipendula, which at the turn of the century was
so abundant there but seems to be dying out, and suggest
that environmental factors have changed. It may be that this
is the reason for the disappearance of some mosses from Essex.
It is interesting to note that although many species of Ortho-
trichum recorded by Varenne (1811-1887) have disappeared,
whilst Leucodon sciuroides and Lejeunea cavifolia are rarely
seen, Orthodontium lineare, which was first recorded in 1946 by
J. H. G. Peterken in Epping Forest, has spread and is quite fre-
quent, pollution and lower humidity notwithstanding.
The boulder clay is richer in its moss flora than the London
clay (Marriott, 1926). South Essex has 190 recorded species
and North Essex has 246. It must be noted, however, that the
former has a smaller area and has been worked by fewer bryolo-